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<body class="manpage">
<div id="header">
<h1>
zmq_getsockopt(3) Manual Page
</h1>
<h2>NAME</h2>
<div class="sectionbody">
<p>zmq_getsockopt -
   get 0MQ socket options
</p>
</div>
</div>
<div id="content">
<div class="sect1">
<h2 id="_synopsis">SYNOPSIS</h2>
<div class="sectionbody">
<div class="paragraph"><p><strong>int zmq_getsockopt (void <em>*socket</em>, int <em>option_name</em>, void <em>*option_value</em>, size_t <em>*option_len</em>);</strong></p></div>
</div>
</div>
<div class="sect1">
<h2 id="_description">DESCRIPTION</h2>
<div class="sectionbody">
<div class="paragraph"><p>The <em>zmq_getsockopt()</em> function shall retrieve the value for the option
specified by the <em>option_name</em> argument for the ØMQ socket pointed to by the
<em>socket</em> argument, and store it in the buffer pointed to by the <em>option_value</em>
argument. The <em>option_len</em> argument is the size in bytes of the buffer pointed
to by <em>option_value</em>; upon successful completion <em>zmq_getsockopt()</em> shall
modify the <em>option_len</em> argument to indicate the actual size of the option
value stored in the buffer.</p></div>
<div class="paragraph"><p>The following options can be retrieved with the <em>zmq_getsockopt()</em> function:</p></div>
<div class="sect2">
<h3 id="_zmq_type_retrieve_socket_type">ZMQ_TYPE: Retrieve socket type</h3>
<div class="paragraph"><p>The <em>ZMQ_TYPE</em> option shall retrieve the socket type for the specified
<em>socket</em>.  The socket type is specified at socket creation time and
cannot be modified afterwards.</p></div>
<div class="hdlist"><table>
<tr>
<td class="hdlist1">
Option value type
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
int
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Option value unit
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
N/A
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Default value
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
N/A
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Applicable socket types
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
all
</p>
</td>
</tr>
</table></div>
</div>
<div class="sect2">
<h3 id="_zmq_rcvmore_more_message_data_parts_to_follow">ZMQ_RCVMORE: More message data parts to follow</h3>
<div class="paragraph"><p>The <em>ZMQ_RCVMORE</em> option shall return True (1) if the message part last
received from the <em>socket</em> was a data part with more parts to follow. If there
are no data parts to follow, this option shall return False (0).</p></div>
<div class="paragraph"><p>Refer to <a href="zmq_send.html">zmq_send(3)</a> and <a href="zmq_recv.html">zmq_recv(3)</a> for a detailed description
of multi-part messages.</p></div>
<div class="hdlist"><table>
<tr>
<td class="hdlist1">
Option value type
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
int
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Option value unit
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
boolean
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Default value
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
N/A
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Applicable socket types
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
all
</p>
</td>
</tr>
</table></div>
</div>
<div class="sect2">
<h3 id="_zmq_sndhwm_retrieves_high_water_mark_for_outbound_messages">ZMQ_SNDHWM: Retrieves high water mark for outbound messages</h3>
<div class="paragraph"><p>The <em>ZMQ_SNDHWM</em> option shall return the high water mark for outbound messages
on the specified <em>socket</em>. The high water mark is a hard limit on the maximum
number of outstanding messages ØMQ shall queue in memory for any single peer
that the specified <em>socket</em> is communicating with.</p></div>
<div class="paragraph"><p>If this limit has been reached the socket shall enter an exceptional state and
depending on the socket type, ØMQ shall take appropriate action such as
blocking or dropping sent messages. Refer to the individual socket descriptions
in <a href="zmq_socket.html">zmq_socket(3)</a> for details on the exact action taken for each socket
type.</p></div>
<div class="hdlist"><table>
<tr>
<td class="hdlist1">
Option value type
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
int
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Option value unit
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
messages
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Default value
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
1000
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Applicable socket types
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
all
</p>
</td>
</tr>
</table></div>
</div>
<div class="sect2">
<h3 id="_zmq_rcvhwm_retrieve_high_water_mark_for_inbound_messages">ZMQ_RCVHWM: Retrieve high water mark for inbound messages</h3>
<div class="paragraph"><p>The <em>ZMQ_RCVHWM</em> option shall return the high water mark for inbound messages on
the specified <em>socket</em>. The high water mark is a hard limit on the maximum
number of outstanding messages ØMQ shall queue in memory for any single peer
that the specified <em>socket</em> is communicating with.</p></div>
<div class="paragraph"><p>If this limit has been reached the socket shall enter an exceptional state and
depending on the socket type, ØMQ shall take appropriate action such as
blocking or dropping sent messages. Refer to the individual socket descriptions
in <a href="zmq_socket.html">zmq_socket(3)</a> for details on the exact action taken for each socket
type.</p></div>
<div class="hdlist"><table>
<tr>
<td class="hdlist1">
Option value type
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
int
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Option value unit
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
messages
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Default value
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
1000
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Applicable socket types
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
all
</p>
</td>
</tr>
</table></div>
</div>
<div class="sect2">
<h3 id="_zmq_affinity_retrieve_i_o_thread_affinity">ZMQ_AFFINITY: Retrieve I/O thread affinity</h3>
<div class="paragraph"><p>The <em>ZMQ_AFFINITY</em> option shall retrieve the I/O thread affinity for newly
created connections on the specified <em>socket</em>.</p></div>
<div class="paragraph"><p>Affinity determines which threads from the ØMQ I/O thread pool associated with
the socket&#8217;s <em>context</em> shall handle newly created connections.  A value of zero
specifies no affinity, meaning that work shall be distributed fairly among all
ØMQ I/O threads in the thread pool. For non-zero values, the lowest bit
corresponds to thread 1, second lowest bit to thread 2 and so on.  For example,
a value of 3 specifies that subsequent connections on <em>socket</em> shall be handled
exclusively by I/O threads 1 and 2.</p></div>
<div class="paragraph"><p>See also <a href="zmq_init.html">zmq_init(3)</a> for details on allocating the number of I/O
threads for a specific <em>context</em>.</p></div>
<div class="hdlist"><table>
<tr>
<td class="hdlist1">
Option value type
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
uint64_t
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Option value unit
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
N/A (bitmap)
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Default value
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
0
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Applicable socket types
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
N/A
</p>
</td>
</tr>
</table></div>
</div>
<div class="sect2">
<h3 id="_zmq_identity_set_socket_identity">ZMQ_IDENTITY: Set socket identity</h3>
<div class="paragraph"><p>The <em>ZMQ_IDENTITY</em> option shall retrieve the identity of the specified <em>socket</em>.
Socket identity is used only by request/reply pattern. Namely, it can be used
in tandem with ROUTER socket to route messages to the peer with specific
identity.</p></div>
<div class="paragraph"><p>Identity should be at least one byte and at most 255 bytes long. Identities
starting with binary zero are reserved for use by ØMQ infrastructure.</p></div>
<div class="hdlist"><table>
<tr>
<td class="hdlist1">
Option value type
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
binary data
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Option value unit
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
N/A
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Default value
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
NULL
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Applicable socket types
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
all
</p>
</td>
</tr>
</table></div>
</div>
<div class="sect2">
<h3 id="_zmq_rate_retrieve_multicast_data_rate">ZMQ_RATE: Retrieve multicast data rate</h3>
<div class="paragraph"><p>The <em>ZMQ_RATE</em> option shall retrieve the maximum send or receive data rate for
multicast transports using the specified <em>socket</em>.</p></div>
<div class="hdlist"><table>
<tr>
<td class="hdlist1">
Option value type
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
int
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Option value unit
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
kilobits per second
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Default value
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
100
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Applicable socket types
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
all, when using multicast transports
</p>
</td>
</tr>
</table></div>
</div>
<div class="sect2">
<h3 id="_zmq_recovery_ivl_get_multicast_recovery_interval">ZMQ_RECOVERY_IVL: Get multicast recovery interval</h3>
<div class="paragraph"><p>The <em>ZMQ_RECOVERY_IVL</em> option shall retrieve the recovery interval for
multicast transports using the specified <em>socket</em>.  The recovery interval
determines the maximum time in milliseconds that a receiver can be absent from a
multicast group before unrecoverable data loss will occur.</p></div>
<div class="hdlist"><table>
<tr>
<td class="hdlist1">
Option value type
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
int
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Option value unit
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
milliseconds
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Default value
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
10000
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Applicable socket types
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
all, when using multicast transports
</p>
</td>
</tr>
</table></div>
</div>
<div class="sect2">
<h3 id="_zmq_sndbuf_retrieve_kernel_transmit_buffer_size">ZMQ_SNDBUF: Retrieve kernel transmit buffer size</h3>
<div class="paragraph"><p>The <em>ZMQ_SNDBUF</em> option shall retrieve the underlying kernel transmit buffer
size for the specified <em>socket</em>. A value of zero means that the OS default is
in effect. For details refer to your operating system documentation for the
<em>SO_SNDBUF</em> socket option.</p></div>
<div class="hdlist"><table>
<tr>
<td class="hdlist1">
Option value type
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
int
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Option value unit
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
bytes
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Default value
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
0
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Applicable socket types
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
all
</p>
</td>
</tr>
</table></div>
</div>
<div class="sect2">
<h3 id="_zmq_rcvbuf_retrieve_kernel_receive_buffer_size">ZMQ_RCVBUF: Retrieve kernel receive buffer size</h3>
<div class="paragraph"><p>The <em>ZMQ_RCVBUF</em> option shall retrieve the underlying kernel receive buffer
size for the specified <em>socket</em>. A value of zero means that the OS default is
in effect. For details refer to your operating system documentation for the
<em>SO_RCVBUF</em> socket option.</p></div>
<div class="hdlist"><table>
<tr>
<td class="hdlist1">
Option value type
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
int
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Option value unit
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
bytes
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Default value
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
0
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Applicable socket types
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
all
</p>
</td>
</tr>
</table></div>
</div>
<div class="sect2">
<h3 id="_zmq_linger_retrieve_linger_period_for_socket_shutdown">ZMQ_LINGER: Retrieve linger period for socket shutdown</h3>
<div class="paragraph"><p>The <em>ZMQ_LINGER</em> option shall retrieve the linger period for the specified
<em>socket</em>.  The linger period determines how long pending messages which have
yet to be sent to a peer shall linger in memory after a socket is closed with
<a href="zmq_close.html">zmq_close(3)</a>, and further affects the termination of the socket&#8217;s
context with <a href="zmq_term.html">zmq_term(3)</a>. The following outlines the different
behaviours:</p></div>
<div class="ulist"><ul>
<li>
<p>
The default value of <em>-1</em> specifies an infinite linger period. Pending
  messages shall not be discarded after a call to <em>zmq_close()</em>; attempting to
  terminate the socket&#8217;s context with <em>zmq_term()</em> shall block until all
  pending messages have been sent to a peer.
</p>
</li>
<li>
<p>
The value of <em>0</em> specifies no linger period. Pending messages shall be
  discarded immediately when the socket is closed with <em>zmq_close()</em>.
</p>
</li>
<li>
<p>
Positive values specify an upper bound for the linger period in milliseconds.
  Pending messages shall not be discarded after a call to <em>zmq_close()</em>;
  attempting to terminate the socket&#8217;s context with <em>zmq_term()</em> shall block
  until either all pending messages have been sent to a peer, or the linger
  period expires, after which any pending messages shall be discarded.
</p>
<div class="hdlist"><table>
<tr>
<td class="hdlist1">
Option value type
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
int
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Option value unit
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
milliseconds
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Default value
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
-1 (infinite)
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Applicable socket types
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
all
</p>
</td>
</tr>
</table></div>
</li>
</ul></div>
</div>
<div class="sect2">
<h3 id="_zmq_reconnect_ivl_retrieve_reconnection_interval">ZMQ_RECONNECT_IVL: Retrieve reconnection interval</h3>
<div class="paragraph"><p>The <em>ZMQ_RECONNECT_IVL</em> option shall retrieve the initial reconnection interval
for the specified <em>socket</em>.  The reconnection interval is the period ØMQ shall
wait between attempts to reconnect disconnected peers when using
connection-oriented transports. The value -1 means no reconnection.</p></div>
<div class="admonitionblock">
<table><tr>
<td class="icon">
<div class="title">Note</div>
</td>
<td class="content">The reconnection interval may be randomized by ØMQ to prevent
reconnection storms in topologies with a large number of peers per socket.</td>
</tr></table>
</div>
<div class="hdlist"><table>
<tr>
<td class="hdlist1">
Option value type
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
int
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Option value unit
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
milliseconds
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Default value
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
100
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Applicable socket types
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
all, only for connection-oriented transports
</p>
</td>
</tr>
</table></div>
</div>
<div class="sect2">
<h3 id="_zmq_reconnect_ivl_max_retrieve_maximum_reconnection_interval">ZMQ_RECONNECT_IVL_MAX: Retrieve maximum reconnection interval</h3>
<div class="paragraph"><p>The <em>ZMQ_RECONNECT_IVL_MAX</em> option shall retrieve the maximum reconnection
interval for the specified <em>socket</em>.  This is the maximum period ØMQ shall wait
between attempts to reconnect. On each reconnect attempt, the previous interval
shall be doubled untill ZMQ_RECONNECT_IVL_MAX is reached. This allows for
exponential backoff strategy. Default value means no exponential backoff is
performed and reconnect interval calculations are only based on
ZMQ_RECONNECT_IVL.</p></div>
<div class="admonitionblock">
<table><tr>
<td class="icon">
<div class="title">Note</div>
</td>
<td class="content">Values less than ZMQ_RECONNECT_IVL will be ignored.</td>
</tr></table>
</div>
<div class="hdlist"><table>
<tr>
<td class="hdlist1">
Option value type
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
int
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Option value unit
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
milliseconds
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Default value
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
0 (only use ZMQ_RECONNECT_IVL)
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Applicable socket types
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
all, only for connection-oriented transport
</p>
</td>
</tr>
</table></div>
</div>
<div class="sect2">
<h3 id="_zmq_backlog_retrieve_maximum_length_of_the_queue_of_outstanding_connections">ZMQ_BACKLOG: Retrieve maximum length of the queue of outstanding connections</h3>
<div class="paragraph"><p>The <em>ZMQ_BACKLOG</em> option shall retrieve the maximum length of the queue of
outstanding peer connections for the specified <em>socket</em>; this only applies to
connection-oriented transports. For details refer to your operating system
documentation for the <em>listen</em> function.</p></div>
<div class="hdlist"><table>
<tr>
<td class="hdlist1">
Option value type
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
int
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Option value unit
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
connections
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Default value
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
100
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Applicable socket types
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
all, only for connection-oriented transports
</p>
</td>
</tr>
</table></div>
</div>
<div class="sect2">
<h3 id="_zmq_maxmsgsize_maximum_acceptable_inbound_message_size">ZMQ_MAXMSGSIZE: Maximum acceptable inbound message size</h3>
<div class="paragraph"><p>The option shall retrieve limit for the inbound messages. If a peer sends
a message larger than ZMQ_MAXMSGSIZE it is disconnected. Value of -1 means
<em>no limit</em>.</p></div>
<div class="hdlist"><table>
<tr>
<td class="hdlist1">
Option value type
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
int64_t
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Option value unit
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
bytes
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Default value
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
-1
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Applicable socket types
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
all
</p>
</td>
</tr>
</table></div>
</div>
<div class="sect2">
<h3 id="_zmq_multicast_hops_maximum_network_hops_for_multicast_packets">ZMQ_MULTICAST_HOPS: Maximum network hops for multicast packets</h3>
<div class="paragraph"><p>The option shall retrieve time-to-live used for outbound multicast packets.
The default of 1 means that the multicast packets don&#8217;t leave the local network.</p></div>
<div class="hdlist"><table>
<tr>
<td class="hdlist1">
Option value type
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
int
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Option value unit
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
network hops
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Default value
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
1
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Applicable socket types
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
all, when using multicast transports
</p>
</td>
</tr>
</table></div>
</div>
<div class="sect2">
<h3 id="_zmq_rcvtimeo_maximum_time_before_a_socket_operation_returns_with_eagain">ZMQ_RCVTIMEO: Maximum time before a socket operation returns with EAGAIN</h3>
<div class="paragraph"><p>Retrieve the timeout for recv operation on the socket.  If the value is <tt>0</tt>,
<em>zmq_recv(3)</em> will return immediately, with a EAGAIN error if there is no
message to receive. If the value is <tt>-1</tt>, it will block until a message is
available. For all other values, it will wait for a message for that amount
of time before returning with an EAGAIN error.</p></div>
<div class="hdlist"><table>
<tr>
<td class="hdlist1">
Option value type
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
int
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Option value unit
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
milliseconds
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Default value
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
-1 (infinite)
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Applicable socket types
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
all
</p>
</td>
</tr>
</table></div>
</div>
<div class="sect2">
<h3 id="_zmq_sndtimeo_maximum_time_before_a_socket_operation_returns_with_eagain">ZMQ_SNDTIMEO: Maximum time before a socket operation returns with EAGAIN</h3>
<div class="paragraph"><p>Retrieve the timeout for send operation on the socket. If the value is <tt>0</tt>,
<em>zmq_send(3)</em> will return immediately, with a EAGAIN error if the message
cannot be sent. If the value is <tt>-1</tt>, it will block until the message is sent.
For all other values, it will try to send the message for that amount of time
before returning with an EAGAIN error.</p></div>
<div class="hdlist"><table>
<tr>
<td class="hdlist1">
Option value type
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
int
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Option value unit
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
milliseconds
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Default value
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
-1 (infinite)
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Applicable socket types
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
all
</p>
</td>
</tr>
</table></div>
</div>
<div class="sect2">
<h3 id="_zmq_ipv4only_retrieve_ipv4_only_socket_override_status">ZMQ_IPV4ONLY: Retrieve IPv4-only socket override status</h3>
<div class="paragraph"><p>Retrieve the underlying native socket type.  A value of <tt>1</tt> will use IPv4
sockets, while the value of <tt>0</tt> will use IPv6 sockets. An IPv6 socket
lets applications connect to and accept connections from both IPv4 and IPv6
hosts.</p></div>
<div class="hdlist"><table>
<tr>
<td class="hdlist1">
Option value type
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
int
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Option value unit
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
boolean
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Default value
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
1 (true)
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Applicable socket types
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
all, when using TCP transports.
</p>
</td>
</tr>
</table></div>
</div>
<div class="sect2">
<h3 id="_zmq_delay_attach_on_connect_retrieve_attach_on_connect_value">ZMQ_DELAY_ATTACH_ON_CONNECT: Retrieve attach-on-connect value</h3>
<div class="paragraph"><p>Retrieve the state of the attach on connect value. If set to <tt>1</tt>, will delay the
attachment of a pipe on connect until the underlying connection has completed.
This will cause the socket to block if there are no other connections, but will
prevent queues from filling on pipes awaiting connection.</p></div>
<div class="hdlist"><table>
<tr>
<td class="hdlist1">
Option value type
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
int
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Option value unit
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
boolean
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Default value
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
0 (false)
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Applicable socket types
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
all, primarily when using TCP/IPC transports.
</p>
</td>
</tr>
</table></div>
</div>
<div class="sect2">
<h3 id="_zmq_fd_retrieve_file_descriptor_associated_with_the_socket">ZMQ_FD: Retrieve file descriptor associated with the socket</h3>
<div class="paragraph"><p>The <em>ZMQ_FD</em> option shall retrieve the file descriptor associated with the
specified <em>socket</em>. The returned file descriptor can be used to integrate the
socket into an existing event loop; the ØMQ library shall signal any pending
events on the socket in an <em>edge-triggered</em> fashion by making the file
descriptor become ready for reading.</p></div>
<div class="admonitionblock">
<table><tr>
<td class="icon">
<div class="title">Note</div>
</td>
<td class="content">The ability to read from the returned file descriptor does not
necessarily indicate that messages are available to be read from, or can be
written to, the underlying socket; applications must retrieve the actual event
state with a subsequent retrieval of the <em>ZMQ_EVENTS</em> option.</td>
</tr></table>
</div>
<div class="admonitionblock">
<table><tr>
<td class="icon">
<div class="title">Note</div>
</td>
<td class="content">The returned file descriptor is also used internally by the <em>zmq_send</em>
and <em>zmq_recv</em> functions. As the descriptor is edge triggered, applications
must update the state of <em>ZMQ_EVENTS</em> after each invocation of <em>zmq_send</em>
or <em>zmq_recv</em>.To be more explicit: after calling <em>zmq_send</em> the socket may
become readable (and vice versa) without triggering a read event on the
file descriptor.</td>
</tr></table>
</div>
<div class="admonitionblock">
<table><tr>
<td class="icon">
<div class="title">Caution</div>
</td>
<td class="content">The returned file descriptor is intended for use with a <em>poll</em> or
similar system call only. Applications must never attempt to read or write data
to it directly, neither should they try to close it.</td>
</tr></table>
</div>
<div class="hdlist"><table>
<tr>
<td class="hdlist1">
Option value type
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
int on POSIX systems, SOCKET on Windows
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Option value unit
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
N/A
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Default value
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
N/A
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Applicable socket types
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
all
</p>
</td>
</tr>
</table></div>
</div>
<div class="sect2">
<h3 id="_zmq_events_retrieve_socket_event_state">ZMQ_EVENTS: Retrieve socket event state</h3>
<div class="paragraph"><p>The <em>ZMQ_EVENTS</em> option shall retrieve the event state for the specified
<em>socket</em>.  The returned value is a bit mask constructed by OR&#8217;ing a combination
of the following event flags:</p></div>
<div class="dlist"><dl>
<dt class="hdlist1">
<strong>ZMQ_POLLIN</strong>
</dt>
<dd>
<p>
Indicates that at least one message may be received from the specified socket
without blocking.
</p>
</dd>
<dt class="hdlist1">
<strong>ZMQ_POLLOUT</strong>
</dt>
<dd>
<p>
Indicates that at least one message may be sent to the specified socket without
blocking.
</p>
</dd>
</dl></div>
<div class="paragraph"><p>The combination of a file descriptor returned by the <em>ZMQ_FD</em> option being
ready for reading but no actual events returned by a subsequent retrieval of
the <em>ZMQ_EVENTS</em> option is valid; applications should simply ignore this case
and restart their polling operation/event loop.</p></div>
<div class="hdlist"><table>
<tr>
<td class="hdlist1">
Option value type
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
int
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Option value unit
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
N/A (flags)
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Default value
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
N/A
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Applicable socket types
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
all
</p>
</td>
</tr>
</table></div>
</div>
<div class="sect2">
<h3 id="_zmq_last_endpoint_retrieve_the_last_endpoint_set">ZMQ_LAST_ENDPOINT: Retrieve the last endpoint set</h3>
<div class="paragraph"><p>The <em>ZMQ_LAST_ENDPOINT</em> option shall retrieve the last endpoint bound for
TCP and IPC transports. The returned value will be a string in the form of
a ZMQ DSN. Note that if the TCP host is INADDR_ANY, indicated by a *, then
the returned address will be 0.0.0.0 (for IPv4).</p></div>
<div class="hdlist"><table>
<tr>
<td class="hdlist1">
Option value type
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
character string
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Option value unit
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
N/A
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Default value
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
NULL
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Applicable socket types
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
all, when binding TCP or IPC transports
</p>
</td>
</tr>
</table></div>
</div>
<div class="sect2">
<h3 id="_zmq_tcp_keepalive_override_so_keepalive_socket_option">ZMQ_TCP_KEEPALIVE: Override SO_KEEPALIVE socket option</h3>
<div class="paragraph"><p>Override <em>SO_KEEPALIVE</em> socket option(where supported by OS).
The default value of <tt>-1</tt> means to skip any overrides and leave it to OS default.</p></div>
<div class="hdlist"><table>
<tr>
<td class="hdlist1">
Option value type
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
int
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Option value unit
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
-1,0,1
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Default value
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
-1 (leave to OS default)
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Applicable socket types
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
all, when using TCP transports.
</p>
</td>
</tr>
</table></div>
</div>
<div class="sect2">
<h3 id="_zmq_tcp_keepalive_idle_override_tcp_keepcnt_or_tcp_keepalive_on_some_os">ZMQ_TCP_KEEPALIVE_IDLE: Override TCP_KEEPCNT(or TCP_KEEPALIVE on some OS)</h3>
<div class="paragraph"><p>Override <em>TCP_KEEPCNT</em>(or <em>TCP_KEEPALIVE</em> on some OS) socket option(where supported by OS).
The default value of <tt>-1</tt> means to skip any overrides and leave it to OS default.</p></div>
<div class="hdlist"><table>
<tr>
<td class="hdlist1">
Option value type
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
int
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Option value unit
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
-1,&gt;0
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Default value
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
-1 (leave to OS default)
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Applicable socket types
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
all, when using TCP transports.
</p>
</td>
</tr>
</table></div>
</div>
<div class="sect2">
<h3 id="_zmq_tcp_keepalive_cnt_override_tcp_keepcnt_socket_option">ZMQ_TCP_KEEPALIVE_CNT: Override TCP_KEEPCNT socket option</h3>
<div class="paragraph"><p>Override <em>TCP_KEEPCNT</em> socket option(where supported by OS).
The default value of <tt>-1</tt> means to skip any overrides and leave it to OS default.</p></div>
<div class="hdlist"><table>
<tr>
<td class="hdlist1">
Option value type
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
int
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Option value unit
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
-1,&gt;0
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Default value
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
-1 (leave to OS default)
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Applicable socket types
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
all, when using TCP transports.
</p>
</td>
</tr>
</table></div>
</div>
<div class="sect2">
<h3 id="_zmq_tcp_keepalive_intvl_override_tcp_keepintvl_socket_option">ZMQ_TCP_KEEPALIVE_INTVL: Override TCP_KEEPINTVL socket option</h3>
<div class="paragraph"><p>Override <em>TCP_KEEPINTVL</em> socket option(where supported by OS).
The default value of <tt>-1</tt> means to skip any overrides and leave it to OS default.</p></div>
<div class="hdlist"><table>
<tr>
<td class="hdlist1">
Option value type
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
int
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Option value unit
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
-1,&gt;0
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Default value
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
-1 (leave to OS default)
</p>
</td>
</tr>
<tr>
<td class="hdlist1">
Applicable socket types
<br />
</td>
<td class="hdlist2">
<p style="margin-top: 0;">
all, when using TCP transports.
</p>
</td>
</tr>
</table></div>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_return_value">RETURN VALUE</h2>
<div class="sectionbody">
<div class="paragraph"><p>The <em>zmq_getsockopt()</em> function shall return zero if successful. Otherwise it
shall return <tt>-1</tt> and set <em>errno</em> to one of the values defined below.</p></div>
</div>
</div>
<div class="sect1">
<h2 id="_errors">ERRORS</h2>
<div class="sectionbody">
<div class="dlist"><dl>
<dt class="hdlist1">
<strong>EINVAL</strong>
</dt>
<dd>
<p>
The requested option <em>option_name</em> is unknown, or the requested <em>option_len</em> or
<em>option_value</em> is invalid, or the size of the buffer pointed to by
<em>option_value</em>, as specified by <em>option_len</em>, is insufficient for storing the
option value.
</p>
</dd>
<dt class="hdlist1">
<strong>ETERM</strong>
</dt>
<dd>
<p>
The ØMQ <em>context</em> associated with the specified <em>socket</em> was terminated.
</p>
</dd>
<dt class="hdlist1">
<strong>ENOTSOCK</strong>
</dt>
<dd>
<p>
The provided <em>socket</em> was invalid.
</p>
</dd>
<dt class="hdlist1">
<strong>EINTR</strong>
</dt>
<dd>
<p>
The operation was interrupted by delivery of a signal.
</p>
</dd>
</dl></div>
</div>
</div>
<div class="sect1">
<h2 id="_example">EXAMPLE</h2>
<div class="sectionbody">
<div class="listingblock">
<div class="title">Retrieving the high water mark for outgoing messages</div>
<div class="content">
<pre><tt>/* Retrieve high water mark into sndhwm */
int sndhwm;
size_t sndhwm_size = sizeof (sndhwm);
rc = zmq_getsockopt (socket, ZMQ_SNDHWM, &amp;sndhwm, &amp;sndhwm_size);
assert (rc == 0);</tt></pre>
</div></div>
</div>
</div>
<div class="sect1">
<h2 id="_see_also">SEE ALSO</h2>
<div class="sectionbody">
<div class="paragraph"><p><a href="zmq_setsockopt.html">zmq_setsockopt(3)</a>
<a href="zmq_socket.html">zmq_socket(3)</a>
<a href="zmq.html">zmq(7)</a></p></div>
</div>
</div>
<div class="sect1">
<h2 id="_authors">AUTHORS</h2>
<div class="sectionbody">
<div class="paragraph"><p>This ØMQ manual page was written by Martin Sustrik &lt;<a href="mailto:sustrik@250bpm.com">sustrik@250bpm.com</a>&gt; and
Martin Lucina &lt;<a href="mailto:mato@kotelna.sk">mato@kotelna.sk</a>&gt;.</p></div>
</div>
</div>
</div>
<div id="footnotes"><hr /></div>
<div id="footer">
<div id="footer-text">
ØMQ 3.2.5<br />
Last updated 2013-11-13 18:57:23 CET
</div>
</div>
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